Powder coating is a kind of process that uses the principle of electrostatic spraying to adsorb the dry powder-like material on the metal aluminum profile after high temperature grilling above 200℃ and then the powder-like material is cured into a layer of solid and bright coating about 60 microns thick.
Powder coating has the advantages of environmental protection, energy saving, durability and beauty, and is widely used in automobile, home appliance, construction, machinery and other fields.
In powder coating, the baking and curing temperature and time of the powder coating play a decisive role in the curing performance of the coating film². If the temperature is too low or the time is too short, it will lead to incomplete curing of the coating film, affecting the adhesion, hardness, weatherability and other properties; if the temperature is too high or the time is too long, it will lead to excessive curing of the coating film, cracking, discoloration, hanging and other defects.
Therefore, when powder coating, it is necessary to reasonably determine the number of pendants and arrangement according to the material, shape and size of the object being coated, and determine the corresponding baking temperature and time through several tests. Generally speaking, the commonly used powder coating curing conditions are 180-200 ℃ / 15-20 minutes.
In addition to controlling the curing temperature and time, attention should also be paid to timely moisture drying after pretreatment to prevent moisture residue caused by bubbles or rust spots; at the same time, before electrostatic spraying to ensure that the surface of the object being sprayed is clean and free of oil to improve the powder adsorption effect; in addition, after curing to timely under the piece and check the quality to avoid leakage of plastic or defects.
When choosing the right oven, take into account the size, shape and number of objects to be sprayed, and choose the appropriate exhaust gas treatment equipment according to the type of exhaust gas it produces. Generally speaking, there are two common types of ovens: continuous and intermittent. Continuous ovens are suitable for mass production with small and regular product size; intermittent ovens are suitable for small mass production with large and irregular product size. Continuous ovens have the advantages of energy saving, high efficiency and small footprint; intermittent ovens have the advantages of flexibility, convenience and large adjustable range.
In selecting the appropriate heating method, the material characteristics of the object to be sprayed and the temperature uniformity to be achieved should be taken into account, and the appropriate heating method should be selected based on the heat exchange relationship between it and the air. Generally speaking, there are two common heating methods: resistance heating and infrared heating. Resistance heating uses the heat generated by the electric current through the heating tube to heat the air, which is then sent into the furnace chamber through a fan; infrared heating uses infrared rays emitted by an emitter to directly heat the object by radiation. Resistance heating has the advantages of uniform temperature and fast response; infrared heating has the advantages of energy saving and high efficiency, strong penetration, etc.
In summary, curing and drying has an important role and influence on the effect of powder coating, and it is necessary to choose the appropriate curing conditions, pre-treatment methods, hanging methods, oven types and heating methods according to different situations in order to ensure the quality and efficiency of powder coating.